JP5786970B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to control a supercharger-equipped internal combustion engine that includes a turbocharger and a wastegate valve that opens and closes an exhaust bypass passage that bypasses the turbine of the turbocharger. Relates to the device.

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine with a turbocharger that includes a waste gate valve that opens and closes an exhaust bypass passage that bypasses a turbine. In this conventional control device, when the accelerator pedal is operated to a predetermined operation amount, the throttle valve is opened to a substantially fully opened position. In addition, when the accelerator pedal is operated to an opening larger than the predetermined operation amount, the waste gate valve is opened so that a target boost pressure corresponding to the detected operation amount of the accelerator pedal and the engine speed is obtained. The supercharging pressure is controlled by adjusting the degree.

  By the way, in an internal combustion engine equipped with a turbocharger, when the atmospheric pressure is low, such as at high altitudes, the intake air amount (equivalent to an equivalent intake air amount (for example, a standard state such as 1 atm) is higher than when the atmospheric pressure is high (for example, a standard state such as 1 atmosphere) The pressure ratio (outlet pressure / inlet pressure) of the compressor of the turbocharger in a state where the engine load factor is obtained becomes high. That is, under the condition where the atmospheric pressure is low, the control range of the intake pressure by the turbocharger when obtaining the same supercharging pressure is larger than in the state where the atmospheric pressure is high. In general, the response of the intake air amount control by the turbocharger is lower than the response of the intake air amount control by the throttle valve.

According to the technique described in Patent Document 1 described above, when the accelerator pedal is operated to an opening larger than the predetermined operation amount, the boost pressure (intake air amount) is adjusted using the opening adjustment of the waste gate valve. ) Is controlled. That is, in this case, since the control allowance for the intake air amount (intake pipe pressure) by the throttle valve cannot be secured, intake air amount control depending on the turbocharger having low response is executed. Under low atmospheric pressure, the throttle opening required to obtain the same intake air amount (engine load factor) is larger than in the standard state. For this reason, under low atmospheric pressure, the load factor region in which the intake air amount control depending on the turbocharger needs to be performed becomes larger than that in the standard state. As a result, under low atmospheric pressure, the responsiveness of the intake air amount during acceleration tends to be lower than in the standard state.
The applicant has recognized the following documents including the above-mentioned documents as related to the present invention.

Japanese Unexamined Patent Publication No. 5-141258 Japanese Unexamined Patent Publication No. 2010-14050 Japanese Unexamined Patent Publication No. 2006-152821 Japanese Unexamined Patent Publication No. 2006-125352 Japanese Unexamined Patent Publication No. 2004-124745 Japanese Unexamined Patent Publication No. 9-53457 Japanese Unexamined Patent Publication No. 2002-213247

  The present invention has been made to solve the above-described problems, and includes a turbocharger and a wastegate valve that opens and closes an exhaust bypass passage that bypasses the turbine of the turbocharger. An object of the present invention is to provide a control device for an internal combustion engine that can improve the responsiveness of the intake air amount during acceleration under low atmospheric pressure.

The present invention is a control device for an internal combustion engine, comprising a turbocharger, a throttle valve, an exhaust bypass passage, a waste gate valve, a steady characteristic switching means, a first throttle control means, and a second throttle control. Means and WGV control means.
The turbocharger includes a compressor that is disposed in the intake passage and supercharges intake air, and a turbine that is disposed in the exhaust passage and operates by exhaust energy.
The throttle valve is disposed in the intake passage and adjusts the intake air amount.
The exhaust bypass passage is configured to branch from the exhaust passage on the upstream side of the turbine and to rejoin the exhaust passage on the downstream side of the turbine.
The waste gate valve is configured to be able to open and close the exhaust bypass passage.
The steady characteristic switching means is a steady characteristic that defines the relationship between the engine load factor and the throttle opening in the steady state. A low atmospheric pressure steady state characteristic that is used under a low atmospheric pressure that is less than or equal to the predetermined value, and depending on whether atmospheric pressure is higher than the predetermined value, the high atmospheric pressure steady state characteristic and the low atmospheric pressure The steady-state characteristic is switched between the steady-state characteristics at atmospheric pressure.
The first throttle control means is configured to select the high atmospheric pressure steady characteristic or the low atmospheric pressure selected by the steady characteristic switching means when a request is made to increase the intake air amount at a change speed lower than a predetermined speed. The throttle opening is controlled so that the target throttle opening obtained based on the steady characteristics and the target engine load factor in this case is obtained.
The second throttle control means is configured to select the low atmospheric pressure selected by the steady-state characteristic switching means when a request is made to increase the intake air amount at a change speed equal to or higher than the predetermined speed under the low atmospheric pressure. The throttle opening is controlled so that the target throttle opening is larger than the value obtained based on the steady state characteristics and the target engine load factor in this case.
The steady state characteristic at low atmospheric pressure is such that the throttle opening corresponding to the same engine load factor is set smaller in the medium load factor region than the steady property at high atmospheric pressure, and the load is higher than in the medium load factor region. The throttle opening is set so as to increase as the engine load factor increases toward the full load in the rate-side region.
Further, the WGV control means has a smaller throttle opening corresponding to the same engine load factor in the medium load factor region than in the high atmospheric pressure steady property in a situation where the low atmospheric pressure steady property is used. Along with the control, the opening degree of the waste gate valve is controlled to a value on the closing side.

  According to the present invention, depending on whether or not the atmospheric pressure is higher than the predetermined value, the steady characteristics that define the relationship between the engine load factor and the throttle opening are the steady characteristics at the high atmospheric pressure and the steady characteristics at the low atmospheric pressure. Switch between properties. When there is no request for an increase in the intake air amount at the predetermined speed or higher under the low atmospheric pressure, the throttle opening is controlled according to the steady characteristic at the low atmospheric pressure. Thereby, a control allowance for the intake air amount (intake pipe pressure) by the throttle valve is ensured in the medium load factor to high load factor region. For this reason, when the increase request | requirement of the intake air amount above the predetermined speed is issued after that, the intake air amount can be controlled using the secured control allowance by the throttle valve. As a result, if the low-atmospheric pressure steady-state characteristic is not obtained, the responsiveness is relatively low at low atmospheric pressure, where the control dependence of the intake air amount to the turbocharger with low response is high. By controlling the intake air amount with a high throttle valve, the response of the intake air amount during acceleration from the medium load factor to the high load factor region can be improved.

Further, the second throttle control means in the present invention may limit the operating speed of the throttle valve so as not to exceed a predetermined upper limit value when the throttle opening is enlarged.
As a result, expansion of the throttle opening at an excessive operating speed does not cause a decrease in the compressor outlet pressure at the initial stage of acceleration, and when the increase in the intake air amount is requested, the response speed of the intake air amount is the fastest and the compressor outlet pressure and The throttle downstream pressure can be raised toward the target value.

Further, the low atmospheric pressure steady state characteristic of the present invention may be set so that the throttle opening becomes smaller as the engine load factor becomes higher in the medium load factor region.
As a result, the control allowance for the intake air amount (intake pipe pressure) by the throttle valve can be further ensured in an area that is equal to or greater than the medium load factor area. As a result, the response of the intake air amount can be further improved when a request to increase the intake air amount at the predetermined speed or higher is issued under a low atmospheric pressure.

It is a schematic diagram for demonstrating the system configuration | structure of the internal combustion engine of Embodiment 1 of this invention. FIG. 4 is a diagram for explaining a problem related to the response of the intake air amount during acceleration under a low atmospheric pressure, and is referred to for comparison with the setting of steady characteristics in the first embodiment of the present invention shown in FIG. 3. It represents the characteristics. It is a figure for demonstrating the two types of load factor-throttle steady state characteristic and load factor-WGV steady state characteristic switched according to the level of atmospheric pressure in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a time chart for demonstrating the control performed in Embodiment 2 of this invention when the increase request | requirement of the intake air amount by a high response is issued under low atmospheric pressure. It is a figure showing the load factor-throttle steady state characteristic and load factor-WGV steady state characteristic which are used in Embodiment 3 of this invention.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a schematic diagram for explaining a system configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The system of this embodiment includes a spark ignition type internal combustion engine (a gasoline engine as an example) 10. A combustion chamber 12 is formed in the cylinder of the internal combustion engine 10. An intake passage 14 and an exhaust passage 16 communicate with the combustion chamber 12.

  An air cleaner 18 is attached in the vicinity of the inlet of the intake passage 14. An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 14 is provided in the vicinity of the downstream side of the air cleaner 18. A compressor 22 a of the turbocharger 22 is installed downstream of the air flow meter 20. The compressor 22a is integrally connected to a turbine 22b disposed in the exhaust passage 16 via a connecting shaft (not shown).

  An intercooler 24 that cools the compressed air is provided downstream of the compressor 22a. An electronically controlled throttle valve 26 is provided downstream of the intercooler 24. In the vicinity of the throttle valve 26, a throttle opening sensor 28 for detecting the throttle opening is attached. A throttle upstream pressure sensor 30 for detecting the intake pressure (throttle upstream pressure) at this portion is attached to the intake passage 14 upstream of the throttle valve 26 and downstream of the compressor 22a (and the intercooler 24). In addition, a throttle downstream pressure sensor 32 for detecting the intake pressure (throttle downstream pressure) at this portion is attached to the intake passage 14 (collection portion (surge tank portion) of the intake manifold) on the downstream side of the throttle valve 26. ing.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 34 for injecting fuel into the cylinder and an ignition device 36 for igniting the air-fuel mixture. Further, the exhaust passage 16 is connected to an exhaust bypass passage 38 configured to branch from the exhaust passage 16 at a portion upstream of the turbine 22b and to rejoin the exhaust passage 16 downstream of the turbine 22b. ing. A waste gate valve (WGV) 40 that can open and close the exhaust bypass passage 38 is provided in the middle of the exhaust bypass passage 38. Here, it is assumed that the WGV 40 is configured to be adjustable to an arbitrary opening degree by an electric motor (not shown).

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. In addition to the air flow meter 20, the throttle opening sensor 28, the throttle upstream pressure sensor 30, and the throttle downstream pressure sensor 32, the ECU 50 includes a crank angle sensor 52 for detecting the engine speed and the crank angle, an engine coolant temperature, and the like. Various sensors for detecting the operating state of the internal combustion engine 10 such as a water temperature sensor 54 for detecting the above are connected. Further, the ECU 50 includes an atmospheric pressure sensor 56 for detecting the atmospheric pressure, and an accelerator opening sensor 58 for detecting the amount of depression of the accelerator pedal (accelerator opening) of the vehicle on which the internal combustion engine 10 is mounted. It is connected. The ECU 50 is connected to various actuators for controlling the operating state of the internal combustion engine 10 such as the throttle valve 26, the fuel injection valve 34, the ignition device 36, and the WGV 40 described above. The ECU 50 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above.

[Problems related to responsiveness of intake air volume during acceleration under low atmospheric pressure]
FIG. 2 is a diagram for explaining a problem relating to the responsiveness of the intake air amount at the time of acceleration under a low atmospheric pressure, for comparison with the setting of steady characteristics (see FIG. 3 described later) in the present embodiment. It represents the steady characteristics to be referred to. More specifically, FIG. 2 is at a predetermined engine speed. FIG. 2A is a diagram showing steady characteristics between the engine load factor KL and the intake pipe pressure (the throttle upstream pressure and the throttle downstream pressure) under a low atmospheric pressure. FIG. 2B is a diagram showing a steady characteristic between the engine load factor KL and the WGV opening degree (hereinafter simply referred to as “load factor—WGV steady characteristic”). FIG. 2C is a diagram showing a steady characteristic (hereinafter simply referred to as “load factor-throttle steady characteristic”) between the engine load factor KL and the throttle opening. The waveform indicated by the broken line in FIG. 2 is obtained when the atmospheric pressure is in the standard state (approximately 1 atm), and the waveform indicated by the solid line in FIG. Atmospheric pressure. The engine load factor KL here is the ratio of the current intake air amount to the maximum intake air amount (intake air amount at full load) corresponding to each engine speed, and the intake air amount. And the engine speed can be calculated.

  As indicated by the “broken line” in FIG. 2C, the load factor-throttle steady state characteristic in the standard state indicates that the throttle opening degree (here, as the shift from the extremely low load factor region to the region on the high load factor side). As an example, with a constant rate of change), the throttle opening is set to be constant at the fully opened position after reaching the fully opened position (maximum opening for control). Has been. On the other hand, as indicated by a “broken line” in FIG. 2B, the load factor-WGV steady state characteristic in the standard state indicates that the WGV opening is smaller in the region on the low load factor side where the throttle opening is smaller than the fully opened opening. In a region on the high load factor side after the predetermined maximum opening (maximum value in the predetermined control range of the WGV opening) and the throttle opening reaches the fully open position, the WGV opening is small (closed side). In this way, the intake air amount that realizes each engine load factor KL can be obtained by using the control of the WGV opening degree.

  The steady state characteristic set based on the same idea as the steady state characteristic in the standard state described above for the low atmospheric pressure condition where the atmospheric pressure is lower than that in the standard state is as follows. That is, in the case where the intake air amount is adjusted using the throttle valve 26 under a low atmospheric pressure, in order to obtain the same intake air amount (engine load factor KL) as in the standard state, the throttle is compared with the standard state. It is necessary to widen the opening. For this reason, as indicated by a “solid line” in FIG. 2C, in the region on the low load factor side of the load factor-throttle steady state characteristic under low atmospheric pressure, the engine load factor is higher than the standard state. As KL increases, the throttle opening is largely controlled toward the fully open opening. As a result, the engine load factor KL at which the throttle opening reaches the fully open opening becomes a value on the low load factor side as compared with the standard state. Accordingly, as indicated by a “solid line” in FIG. 2B, the load factor-WGV steady state characteristic under a low atmospheric pressure starts to close at a lower engine load factor KL than in the standard state. Therefore, the WGV opening degree is controlled.

  In the case of having the above-mentioned steady characteristics under a low atmospheric pressure, as shown in FIG. 2A, the throttle downstream pressure increases the throttle opening or WGV opening as the engine load factor KL increases. As the degree decreases, it rises. On the other hand, the throttle upstream pressure in this case is constant at the atmospheric pressure value in this case because the WGV 40 is sufficiently opened and supercharging is not performed in the region until the throttle opening reaches the full opening. Transition to. Thereafter, supercharging is started and increases with an increase in the engine load factor KL at a value substantially equal to the throttle downstream pressure. Note that the steady characteristics of the throttle upstream pressure and the downstream pressure with respect to the engine load factor KL are the same in trend, although there are differences in values even under standard atmospheric pressure.

  Incidentally, in an internal combustion engine equipped with a turbocharger, such as the internal combustion engine 10 of the present embodiment, the intake air amount equivalent to a high atmospheric pressure, such as a high altitude, compared to a high atmospheric pressure (standard state). The pressure ratio (outlet pressure / inlet pressure) of the compressor of the turbocharger in a state where (engine load factor KL) is obtained increases. That is, under the condition where the atmospheric pressure is low, the control range of the intake pressure by the turbocharger when obtaining the same supercharging pressure is larger than that in the standard state. In general, the response of the intake air amount control by the turbocharger is lower than the response of the intake air amount control by the throttle valve.

  According to the setting of the load factor-throttle steady characteristic shown in FIG. 2 above, in the region on the higher load factor side than the engine load factor KL at which the throttle opening reaches the fully open opening, the suction is performed using the opening adjustment of the WGV 40. The amount of air (supercharging pressure) is controlled. That is, in the above steady characteristics, the control allowance for the intake air amount (intake pipe pressure) by the throttle valve 26 is ensured in the region on the higher load factor side than the engine load factor KL when the throttle opening reaches the fully open opening. Therefore, the intake air amount control depending on the turbocharger 22 having low responsiveness is executed. Under low atmospheric pressure, as shown in FIG. 2, the load factor region in which it is necessary to perform intake air amount control depending on the turbocharger 22 is larger than that in the standard state, as compared with the standard state. . For this reason, under low atmospheric pressure, the responsiveness of the intake air amount during acceleration tends to be lower than in the standard state.

[Characteristic Load Factor-Throttle Steady Characteristics and Load Factor-WGV Steady Characteristics Settings in Embodiment 1]
FIG. 3 is a diagram for explaining two types of load factor-throttle steady characteristic and load ratio-WGV steady characteristic that are switched according to the level of atmospheric pressure in the first embodiment of the present invention. More specifically, FIG. 3 is at a predetermined engine speed. FIG. 3A is a diagram showing steady characteristics between the engine load factor KL and the intake pipe pressure (the throttle upstream pressure and the throttle downstream pressure) under a low atmospheric pressure. FIG. 3B is a diagram showing the load factor-WGV steady state characteristic. FIG. 3C is a diagram showing the load factor-throttle steady characteristic. The waveform indicated by the broken line in FIG. 3 is obtained when the atmospheric pressure is in the standard state (approximately 1 atm), and the waveform indicated by the solid line in FIG. Atmospheric pressure. The steady characteristics shown in FIGS. 3B and 3C change according to the engine speed. For this reason, in the present embodiment, as these steady-state characteristics, the setting tendency itself is the same as that shown in FIG. 3 below for each predetermined engine speed.

  As indicated by a broken line in FIG. 3, the load factor-throttle steady characteristic (hereinafter sometimes referred to as “throttle characteristic at high atmospheric pressure”) in a state where the atmospheric pressure is higher than a predetermined value (standard state) and The load factor-WGV steady characteristics (WGV steady characteristics at high atmospheric pressure) are the same as those shown in FIG.

On the other hand, the load factor-throttle steady state characteristic (hereinafter sometimes referred to as “throttle steady state characteristic at low atmospheric pressure”) in a low atmospheric pressure state where the atmospheric pressure is equal to or lower than the predetermined value is shown in FIG. As described above, in the load factor region (KL5 to KL3) included in the medium load factor region (KL1 to KL3) , the throttle opening corresponding to the same engine load factor KL is set smaller than the steady state characteristic of the throttle at high atmospheric pressure. ing. Further, the steady-state characteristics of the throttle at low atmospheric pressure indicate that the engine load factor KL increases toward the full load (KL4) in the region (KL3 to KL4 (100%)) on the higher load factor side than the intermediate load factor region. The throttle opening is set so as to increase toward the fully open position. More specifically, in the example shown in FIG. 3, the throttle opening in the medium load factor region (KL1 to KL3) including the load factor region (KL5 to KL3) is a predetermined constant opening TA1 that is smaller than the fully opened opening. Is set to In the low load factor region lower than the engine load factor KL1, the reason why the change rate of the throttle opening with respect to the engine load factor KL is set higher at the low atmospheric pressure than in the standard state is as described above. In addition, in order to obtain the same intake air amount (engine load factor KL) as in the standard state, it is necessary to control the throttle opening to a greater extent than in the standard state.

  Further, in the low atmospheric pressure steady state characteristic of WGV, the low load factor side end characteristic (KL1) of the medium load factor region (KL1 to KL3) where the adjustment of the throttle opening is stopped is the WGV high atmospheric pressure steady state characteristic. The WGV 40 is set so as to start to close from the engine load factor KL on the lower load factor side. The WGV opening in the medium load factor region (KL1 to KL3) is more largely closed as the engine load factor KL increases while the throttle opening is constant. This is to compensate for the insufficient intake air amount compared to the standard state due to the steady characteristic of the throttle at low atmospheric pressure. Further, the WGV opening in the region (KL3 to KL4) on the higher load factor side than the middle load factor region is approximately the value at the engine load factor KL3 (a predetermined value opened from the surge line of the compressor 22a). It is set to be constant.

  As shown in FIG. 3 (A), the throttle downstream pressure when the throttle and WGV steady-state characteristics at low atmospheric pressure are used increases the throttle opening or the WGV opening as the engine load factor KL increases. It rises with the decrease of. On the other hand, the throttle upstream pressure in this case remains constant at the atmospheric pressure value in this case because supercharging is not performed until the engine load factor KL1 at which the WGV 40 starts to close is reached. Thereafter, as the WGV 40 is closed, the turbine rotational speed becomes higher and supercharging proceeds. That is, according to this setting, at the engine load factor KL1 corresponding to the throttle opening TA1 smaller than the fully opened opening, expansion of the throttle opening corresponding to the increase in the engine load factor KL is stopped, and the WGV 40 starts to close. As a result, unlike the setting shown in FIG. 2, a significant difference is ensured between the throttle upstream pressure and the throttle downstream pressure.

  In the example shown in FIG. 3, in the middle load factor region (KL1 to KL3), the WGV 40 is closed as the engine load factor KL increases instead of adjusting the opening of the throttle valve 26. Therefore, the difference between the throttle upstream pressure and the throttle downstream pressure is maintained. Also in the region on the higher load factor side than the medium load factor region (KL1 to KL3), the throttle upstream pressure rises as the engine load factor KL increases. However, since the WGV opening is substantially constant and the throttle valve 26 is opened, the throttle upstream pressure in this region becomes more gradual than in the medium load factor region (KL1 to KL3) as the engine load factor KL increases. To rise. Further, in this region, since the throttle valve 26 is set to be opened toward the fully open position as the engine load factor KL increases, the throttle upstream pressure and the throttle valve are increased as the throttle opening increases. The difference with the downstream pressure becomes smaller.

  As described above, according to the steady characteristic at the time of low atmospheric pressure of the throttle and the WGV in the present embodiment, the throttle opening is determined from the medium load factor at which the throttle opening is fully opened when the steady characteristic shown in FIG. 2 is used. In the high load factor region, a significant difference between the throttle upstream pressure and the throttle downstream pressure, that is, a control allowance for the intake air amount (intake pipe pressure) by the throttle valve 26 can be secured. Further, according to the low atmospheric pressure steady state characteristic, the turbine rotational speed can be made higher than when the lower load factor side region is used as compared with the high atmospheric pressure steady state characteristic.

  In the present embodiment, when a request to increase the intake air amount at a change speed lower than a predetermined speed is issued (when a slow acceleration is requested), the air pressure is used depending on whether the atmospheric pressure is higher than a predetermined value. The steady characteristics of the throttle and WGV to be switched are switched. Specifically, under high atmospheric pressure (standard state) where the atmospheric pressure is higher than the predetermined value, steady characteristics at high atmospheric pressure of the throttle and WGV (waveforms indicated by broken lines in FIG. 3) are selected, and the atmospheric pressure is Under a low atmospheric pressure that is equal to or lower than the predetermined value, a steady characteristic at low atmospheric pressure (a waveform indicated by a solid line in FIG. 3) of the throttle and WGV is selected. When a request to increase the intake air amount at a change speed lower than the predetermined speed is given (when the slow acceleration is requested), refer to the steady characteristics at the selected high atmospheric pressure or low atmospheric pressure. Then, the target throttle opening and the target WGV opening corresponding to the target engine load factor (target intake air amount) at the time of this acceleration are calculated. Then, throttle valve 26 and WGV 40 are controlled so that these target throttle opening and target WGV opening are obtained.

  On the other hand, in the present embodiment, when a request is made to increase the intake air amount at a changing speed that is equal to or higher than the predetermined speed (when sudden acceleration is requested), the atmospheric pressure is lower than the predetermined value. In this case, the target throttle opening is set to a value larger than the throttle opening obtained by referring to the steady characteristic of the throttle at the low atmospheric pressure as a value corresponding to the target engine load factor (target intake air amount) at the time of this acceleration. The degree is calculated. Further, the target WGV opening in this case is calculated as a value corresponding to the target engine load factor (target intake air amount) at the time of the current acceleration with reference to the steady characteristics of the WGV at the low atmospheric pressure.

  FIG. 4 is a flowchart showing a control routine executed by the ECU 50 in the first embodiment in order to realize the throttle and WGV control described above. This routine is repeatedly executed every predetermined control cycle.

  In the routine shown in FIG. 4, first, the state of the vehicle on which the internal combustion engine 10 is mounted and various parameters indicating the engine state are detected (step 100). Specifically, in the present step 100, the various vehicle sensors shown in FIG. 1 and the various sensors not shown are used, and the vehicle speed and the accelerator opening as the request information from the driver A shift position of a transmission (not shown) is acquired. Further, as the engine state, an engine speed, an intake air amount, an engine coolant temperature, a compression ratio, and the like are acquired.

  Next, it is determined whether the atmospheric pressure is higher than a predetermined value using the atmospheric pressure sensor 56 (step 102). As a result, when it is determined that the atmospheric pressure is higher than the predetermined value, that is, when the atmospheric pressure is in the standard state, for example, based on the accelerator opening and the engine speed, the target engine load factor ( A target intake air amount is calculated (step 104).

  Next, the target throttle opening and the target WGV opening are calculated using the target engine load factor calculated in step 104 and the steady-state characteristics of the throttle and WGV during high atmospheric pressure (the waveforms shown by the broken lines in FIG. 3). Are respectively calculated (step 106). Next, the throttle valve 26 and the WGV 40 are respectively controlled according to the calculated target throttle opening and target WGV opening (step 108).

  On the other hand, if it is determined in step 102 that the atmospheric pressure is in a low atmospheric pressure state where the atmospheric pressure is equal to or lower than the predetermined value, it is then determined whether or not there is a request to increase the intake air amount at the predetermined speed or higher. (Step 110). Specifically, the determination in step 110 is performed by comprehensively determining the amount and speed of depression of the accelerator pedal, the shift position of the transmission, and the like.

  If the determination in step 110 is not established, that is, if the increase in intake air amount with a high response is not requested (when a slow acceleration request is issued), the accelerator opening and the engine speed are Based on the above, a target engine load factor (target intake air amount) is calculated (step 112).

  Next, using the target engine load factor calculated in step 112 and the steady state characteristics of the throttle and WGV during low atmospheric pressure (the waveform shown by the solid line in FIG. 3), the target throttle opening and target WGV open Each degree is calculated (step 114). Next, throttle valve 26 and WGV 40 are respectively controlled according to the calculated target throttle opening and target WGV opening (step 116).

  On the other hand, when the determination in step 110 is satisfied, that is, when an increase in the intake air amount with a high response is requested (when a rapid acceleration request is issued), the target corresponding to the high response request A throttle opening and a target WGV opening are calculated (step 118). Specifically, in step 118, the target throttle opening is set to a value larger than the value calculated by substituting the target engine load factor at the time of the high response request this time into the low atmospheric pressure steady state characteristic. Calculated. For example, the fully opened opening degree is acquired as the target throttle opening degree. The target WGV opening is calculated by substituting the target engine load factor at the time of the high response request this time into the low atmospheric pressure steady state characteristic. However, if the target WGV opening obtained in this case has a margin for the compressor surge on the steady characteristic at low atmospheric pressure in relation to the current target engine load factor, the compressor surge is avoided. It may be the minimum opening that can be obtained. Next, the throttle valve 26 and the WGV 40 are respectively controlled according to the calculated target throttle opening and target WGV opening (step 120).

  According to the routine shown in FIG. 4 described above, the steady characteristic at high atmospheric pressure or the steady characteristic at low atmospheric pressure is selected as the steady characteristic of the throttle and WGV depending on whether the atmospheric pressure is higher than the predetermined value. Is done. When there is no request for an increase in the intake air amount with a high response under low atmospheric pressure, the throttle opening and the WGV opening are controlled according to the steady characteristic at low atmospheric pressure. Thereby, a control allowance for the intake air amount (intake pipe pressure) by the throttle valve 26 is ensured in the medium load factor to high load factor region. For this reason, when a request to increase the amount of intake air with a high response is issued thereafter, the amount of intake air can be controlled using the secured control margin by the throttle valve 26. As a result, if the low atmospheric pressure steady-state characteristic is not obtained, the response to the turbocharger 22 with low response is relatively low under low atmospheric pressure where the control dependence of the intake air amount to the turbocharger 22 is high. By controlling the intake air amount with the highly reliable throttle valve 26, the response of the intake air amount during acceleration from the medium load factor to the high load factor region can be improved.

  Further, according to the routine described above, in a state where the atmospheric pressure is higher than the predetermined value (standard state or the like), unlike the case where the atmospheric pressure is low, the steady state for securing the control amount of the intake air amount by the throttle valve 26 Character setting and control using it are not executed. The control at the time of requesting an increase in the intake air amount with a high response described above under a low atmospheric pressure is a control that deviates from the operating point at which the fuel efficiency is optimal. For this reason, in the present embodiment, such control is performed only at low atmospheric pressure, which has a large effect on the responsiveness of the intake air amount. As described above, in the present embodiment, in the control of the intake air amount using the throttle opening and the WGV opening, it is considered that the frequency of deviation from the optimum fuel efficiency operating point is reduced.

  In Embodiment 1 described above, the throttle opening used in the medium load factor region (KL1 to KL3) under a low atmospheric pressure is set to a predetermined constant opening TA1. By the way, by reducing the throttle opening in the medium load factor region under such a low atmospheric pressure (and by reducing the WGV opening accordingly), the throttle upstream pressure and the throttle downstream pressure This makes it possible to secure a larger control allowance for the intake air amount by the throttle valve 26. However, if the control allowance is secured too much, the result is that the responsiveness of the intake air amount is excessively secured, and the fuel consumption is deteriorated due to the throttle valve 26 being largely closed. Therefore, the throttle opening used in the medium load factor region under the low atmospheric pressure is, for example, before and after the throttle valve 26 in order to prevent excessively responsiveness of the intake air amount under the low atmospheric pressure. The engine load factor KL (intake air amount) increases as the pressure ratio (pressure drop rate) becomes constant at a predetermined value (preferably the current atmospheric pressure / standard atmospheric pressure). It may be set as follows.

  Further, in the first embodiment described above, depending on whether or not the atmospheric pressure is higher than the predetermined value, two types of steady characteristics, that is, a steady characteristic at high atmospheric pressure and a steady characteristic at low atmospheric pressure are used properly. Yes. However, the low atmospheric pressure steady state characteristic used in the present invention under a low atmospheric pressure is not limited to a single setting. That is, the steady state characteristic at low atmospheric pressure in the present invention is stepwise so that, for example, under low atmospheric pressure, when the atmospheric pressure is low, the throttle opening in the medium load factor region is smaller than when the atmospheric pressure is high. It may be set to change to, or continuously set so that the throttle opening in the medium load factor region becomes smaller as the atmospheric pressure becomes lower at low atmospheric pressure. It may be.

In the first embodiment described above, the load factor region (KL5 to KL3) is the same engine in the present invention as compared with the high atmospheric pressure steady property in the low load atmospheric pressure region. This corresponds to the “medium load factor region” in the description that “the throttle opening corresponding to the load factor is set to be small”. Further, the ECU 50 executes one of the processes of the steps 106 and 114 in accordance with the determination result of the step 102, thereby realizing the “steady characteristic switching means” in the present invention. To 108, or the above-described steps 110 to 116, the "first throttle control means" in the present invention is realized, and the ECU 50 performs the above steps 118 and 120 when the determination at step 110 is established. By executing, the “second throttle control means” in the present invention is realized, and when the ECU 50 executes the processing of steps 104 to 108 or steps 118 to 120, the “WGV control means” in the present invention. It has been realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
As a premise, the system of the present embodiment has the hardware configuration shown in FIG. 1 and executes the same control as that of the first embodiment described above. In addition, in this embodiment, the operation speed of the throttle valve 26 as described below is regulated as necessary.

FIG. 5 is a time chart for explaining the control executed in the second embodiment of the present invention when a request for increasing the intake air amount with a high response is issued under a low atmospheric pressure.
According to the control at the low atmospheric pressure in the first embodiment described above, the intake air amount (intake pipe pressure) secured by the throttle valve 26 when a request to increase the intake air amount with a high response is issued. By using the control allowance, it is possible to improve the responsiveness of the intake air amount.

  However, if the opening speed of the throttle valve 26 is too high when a request for increasing the intake air amount with a high response is made, the response speed of the intake air amount will deteriorate as shown below. That is, as shown in FIG. 5D, when the depression of the accelerator pedal that requires rapid acceleration is detected, the target surge tank pressure (throttle downstream pressure) indicated by the broken line in FIG. Therefore, when the throttle opening and the WGV opening are controlled at the maximum operating speed as shown in the thin solid line in FIG. 5C and FIG. 5B, the following problem occurs.

  When both the throttle opening and the WGV opening are operated at the highest speed as described above, the speed at which the throttle valve 26 is opened is too high, and the compressed air downstream of the compressor 22a is increased before the turbine speed increases. Is easily inhaled. As a result, the compressor outlet pressure (≈throttle upstream pressure) decreases at the initial stage of acceleration, as indicated by a thin one-dot chain line in FIG. As shown by a thin solid line in FIG. 5 (A), the surge tank pressure (throttle downstream pressure) rises with good response at the beginning of acceleration, but supercharging cannot catch up, so the subsequent pressure rise temporarily stagnates. End up. By such a phenomenon, the response speed of the intake air amount is deteriorated.

  Therefore, in the present embodiment, when a request to increase the intake air amount with a high response is issued under a low atmospheric pressure, the operation speed of the throttle valve 26 is limited so as not to exceed a predetermined upper limit value. did. Specifically, the operating speed of the throttle valve 26 is limited as shown by a thick solid line in FIG. 5C so as not to cause the above-described decrease in the compressor outlet pressure due to the quick opening of the throttle valve 26. Is done.

  According to the control of the present embodiment described above, as shown by a thick dashed line and a thick solid line in FIG. 5A, when the intake air amount is requested to increase without causing a decrease in the compressor outlet pressure in the initial stage of acceleration. As the response speed of the intake air amount, the compressor outlet pressure and the surge tank pressure can be raised toward the target values at the fastest speed.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a diagram showing the load factor-throttle steady characteristic and the load factor-WGV steady characteristic used in the third embodiment of the present invention. The system according to the present embodiment is the same as the system according to the first embodiment described above except for the points described later with reference to FIG.

In Embodiment 1 (and 2) described above, the throttle opening used in the medium load factor region (KL1 to KL3) under the low atmospheric pressure is set to a predetermined constant opening TA1. On the other hand, in this embodiment, the throttle opening used in the medium load factor region (KL1 to KL3) under the low atmospheric pressure is the engine load factor KL as shown by a thick solid line in FIG. It is set to become smaller as the value becomes higher. Here, the engine load factor KL where the broken line waveform of the throttle opening and the thick solid line waveform in FIG. 6C intersect is referred to as “KL6”. The medium load factor area (KL1 to KL3) includes the load factor area (KL6 to KL3).

  Accordingly, the WGV opening is the engine load factor KL3 on the lower load factor side than the full load (KL4) as shown by the thick solid line in FIG. It is set so that the minimum opening is obtained with a smaller value (close side). More specifically, the WGV opening in the medium load factor region becomes smaller as the engine load factor KL increases toward the minimum opening at the engine load factor KL3. And in the area | region of the high load factor side rather than the said medium load factor area | region, it sets so that the WGV opening degree may become larger, so that the engine load factor KL becomes high.

According to the setting of the steady characteristics described above, the throttle opening used in the medium load factor region (KL1 to KL3) including the load factor region (KL6 to KL3) under the low atmospheric pressure increases as the engine load factor KL increases. It ’s getting smaller. The medium load factor region (KL1 to KL3) is a region where the engine load factor KL (intake air amount) is adjusted mainly by the WGV opening. Therefore, according to the setting of the present embodiment, as compared with the setting of the first embodiment described above, as shown in FIG. 6 (A), the amount of intake air by the throttle valve 26 in the region above the medium load factor region. A larger control allowance for (intake pipe pressure) can be secured. This makes it possible to further improve the responsiveness of the intake air amount when a request is made to increase the intake air amount with a high response under low atmospheric pressure. In the third embodiment described above, the load factor region (KL6 to KL3) in the medium load region (KL1 to KL3) is “the low atmospheric pressure steady state characteristic is in the medium load factor region”. This corresponds to “the medium load factor region” in the description that “the throttle opening is set to be smaller as the engine load factor becomes higher”.

10 Internal combustion engine 12 Combustion chamber 14 Intake passage 16 Exhaust passage 18 Air cleaner 20 Air flow meter 22 Turbocharger 22a Turbocharger compressor 22b Turbocharger turbine 24 Intercooler 26 Throttle valve 28 Throttle opening sensor 30 Throttle upstream Pressure sensor 32 Throttle downstream pressure sensor 34 Fuel injection valve 36 Ignition device 38 Exhaust bypass passage 40 Waste gate valve (WGV)
50 ECU (Electronic Control Unit)
52 Crank angle sensor 54 Water temperature sensor 56 Atmospheric pressure sensor 58 Accelerator opening sensor

Claims (3)

A turbocharger including a compressor disposed in the intake passage and supercharging intake air; and a turbine disposed in the exhaust passage and operating by exhaust energy;
A throttle valve arranged in the intake passage for adjusting the amount of intake air;
An exhaust bypass passage branched from the exhaust passage upstream of the turbine and rejoining the exhaust passage downstream of the turbine;
A waste gate valve capable of opening and closing the exhaust bypass passage;
Steady characteristics that define the relationship between the engine load factor and the throttle opening in a steady state, steady characteristics at high atmospheric pressure used under high atmospheric pressure where the atmospheric pressure is higher than a predetermined value, and the atmospheric pressure is below the predetermined value A low atmospheric pressure steady state characteristic that is used under a low atmospheric pressure, and depending on whether the atmospheric pressure is higher than the predetermined value, the high atmospheric pressure steady state characteristic and the low atmospheric pressure steady state characteristic A stationary characteristic switching means for switching the stationary characteristic between,
When a request is made to increase the intake air amount at a change speed lower than a predetermined speed, the high atmospheric pressure steady characteristic or the low atmospheric pressure steady characteristic selected by the steady characteristic switching means and the target in this case First throttle control means for controlling the throttle opening so as to obtain a target throttle opening obtained based on the engine load factor;
When there is a request to increase the intake air amount at a change speed equal to or higher than the predetermined speed under the low atmospheric pressure, the low atmospheric pressure steady characteristic selected by the steady characteristic switching means and Second throttle control means for controlling the throttle opening so that the target throttle opening is larger than a value obtained based on the target engine load factor;
With
The steady state characteristic at low atmospheric pressure is such that the throttle opening corresponding to the same engine load factor is set smaller in the medium load factor region than the steady property at high atmospheric pressure, and the load is higher than in the medium load factor region. In the rate-side area, the throttle opening is set to increase as the engine load factor increases toward the full load.
In a situation where the low atmospheric pressure steady state characteristic is used, the throttle opening corresponding to the same engine load factor is controlled to be smaller in the medium load factor region than the high atmospheric pressure steady state characteristic. An internal combustion engine control device further comprising WGV control means for controlling the opening of the waste gate valve to a closed value.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the second throttle control means limits the operating speed of the throttle valve so as not to exceed a predetermined upper limit value when the throttle opening is enlarged. .   3. The control of an internal combustion engine according to claim 1, wherein the steady state characteristic at low atmospheric pressure is set such that the throttle opening decreases as the engine load factor increases in the medium load factor region. apparatus.

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